Patent GB-1003152-A (GB)
IPC: B21J9/20
Abstract: 1,003,152. Electric control systems. BRITISH IRON & STEEL CORPORATION. Nov 2, 1961 [Nov. 2, 1960], No. 37674/60. Heading G1N. [Also in Division B3] In a forging operation in which a workpiece is forged to a required shape by press tools in a succession of passes, each pass comprising a plurality of squeezes, the relative longitudinal movement between workpiece and press tools between successive squeezes of a pass (the bite) is controlled at a constant proportion of the initial width of the workpiece at the beginning of the pass; in addition, the reduction achieved during each pass is maintained at a constant proportion of the initial thickness of the workpiece at the beginning of the pass, as described in Specification 901,270. The invention is described mainly with reference to the reduction of a workpiece of square cross-section to a smaller square crosssection. As shown, the crosshead 12 of the forge is controlled by a remote position control system 13 as described in Specification 874,908. The instantaneous position of the crosshead and thus of the upper work tool is measured by a transducer 14, e.g. a potentiometer, the output of which is fed back to control system 13. This output is also supplied to a device 22 which is controlled by a velocity transducer 20 connected to the crosshead 12, through a workpiece surface detector 21, so that the output of device 22 is held at the value of transducer 14 when the upper work tool first engages the workpiece,i.e. it is representative of the initial thickness of the workpiece. The output of device 22 is fed to a multiplier 24 wherein it is multiplied by (1-r), where r is the desired proportional reduction, the product signal therefrom being supplied via a switch unit 26 to a store A or B depending on whether the pass is odd or even, and thence via a switch unit 27 to constitute the lower limit order signal for control system 13. The upper limit order signal is also derived from device 22, a preset value such as one inch being added at 28. A manipulator, controlled as described in Specification 892,216, moves the workpiece longitudinally between squeezes and rotates it through 90 degrees between passes; the latter rotational movement has the effect of making the forged thickness of the workpiece in one pass the initial width of the workpiece in the next pass. The dimension is extracted from store A on even passes and from store B on odd passes, multiplied at 31 or 33 by #, i.e. the set-in ratio of bite to initial width, and used to control the longitudinal movement of the manipulator. For the first pass of a workpiece of square cross-section the initial width is equal to the initial thickness and this latter quantity is fed from switch unit 26 via switches 44 and 34 to store B; if the workpiece is initially rectangular in section, the initial width is set in a store 45. The output of multiplier 24 is continuously compared with a final dimension in a monitor 35; if the final section of the workpiece is rectangular, two dimensions are set into the monitor and the output of the multiplier is compared with each in alternate passes, sequencing being performed by switch unit 27 which also sequences the access of the control system 13 to stores A and B. When the multiplier output is less than the set-in final dimension the monitor 35 operates to open switch 36, thus disconnecting the multiplier from the control system 13, and to supply a final dimension signal to the control system. Operation of a "start" unit 41 connects switch 34 to switch 44; sets store A at zero; sets switch unit 27 to "odd"; and initiates downward movement of the upper work tool. An indicator 38 operates at the end of each pass to unlock device 22; change switch units 26 and 27; initiate appropriate manipulator movements; and, at the end of the first pass, reset switch 34. The transducer used may incorporate digitisers and the initial section of the workpiece may be other than rectangular or square.